Study On Characteristic Of Electromagnetic Waves Propagation And Key Technology In Complicated Coal Mine Tunnels

The basic characteristic of electromagnetic wave propagation in mine laneway is a space-constrained environment. Electromagnetic wave propagation in mine laneway is very influenced by underground environmental factors and human factors seriously, so electromagnetic wave can not be well disseminated in the laneway.This paper researches the propagation characteristics of electromagnetic waves under changeable spatial structure in different laneway, as well as changing environmental parameters impact on propagation attenuation, establishes a common prediction model of electromagnetic wave propagation in mine laneway, which provide reliable arguments for designing of wireless communication systems, improving the reliability and quality of communication, solving technical problems of anti multipath fading. The main contents and research methods in the following areas:(1) Electromagnetic wave propagation characteristics of mine tunnelsMine roadway will be regarded as a waveguide which containing detrimental media, according to waveguide transmission theory, it is proposed to use WGMD (wave-guide mode matching) and Marcatili to analyze a general law of electromagnetic wave propagation in an empty straight roadway, gets the two field-types:those are Emn(h) model and Emn(v) model, derives the transmission constant of propagation model under different boundary conditions, the calculation formula of transmission cut-off frequency and the approximate solution of attenuation rate,据接收机的反馈信息,发射机为发送符号!!EMBED Equation.DSMT4(?)分(2)(?)wironmental factors on the transmission characteristicsThe electromagnetic field intensity distribution which got by the above method is not for the physical environment and the mine roadway with special configuration (Such as the roadway wall is a low-conductivity mine roadway, and includes power cables, rails, locomotives and hydraulic metal backbone of the road, and the curved roadway, etc.). This paper analyzes the electrical parameters of the roadway walls changed with formation pressure, mining depth and material structure, derives the electromagnetic wave mode equation and transfer constants under different conditions according to the characteristics of special-shaped roadway such as class matrix roadway, circular roadway and bended roadway, etc. analyses metal single pillar and transport locomotive made impact on transmission cut-off frequency using finite element method, and numerical simulates the relationship among the roadway cross-section size, communication model of electromagnetic waves and wave-mode cut-off frequency in complex environment of roadway, as well as the relationship between the electromagnetic parameters of changing environment and the attenuation of electromagnetic wave signal to noise ratio.(3) The establishment of Multi-path channel transmission modelAs the underground roadway is limit propagation space, multi-path propagation is the significant characteristics of mine electromagnetic wave propagation because of the rough roadway walls and obstacles which is more important.This paper takes the impact of environmental factors such as the dielectric constant of roadway wall into account, discusses the advantages and disadvantages of the electromagnetic field intensity distribution by using the waveguide mode matching method and ray tracing in predicting roadway, pointes out that the waveguide mode matching method can be applied field strength prediction of the far-field zone, ray-tracing method is more suitable in the near-field area, establishes a near-field zone with multi-path channel prediction model of mine roadway using ray-tracing method, proposes three-dimensional zigzag spiral light transmission path and the calculation method of incident angle and reflection angle, and discusses the changing relationship among the shape of the roadway, transmission frequency and transmission loss.(4) Anti-multi-path fading based on MIMO technologyThis paper analyzes transmission loss properties between large scale and small scale of specific band of electromagnetic waves in class matrix roadway, explores some of the advantages of MIMO technology, which has possibility to be used in wireless communications mine according to the application environment of underground mobile communication terminal, signal processing complexity and portability requirements, proposes the idea of using the array structure of sending and receiving ends of MIMO technology to enhance the anti-fading performance of mine wireless communication systems and establishes two mine MIMO channel models. This paper also analyzes spatial correlation of the transceiver antenna which has effect on system performance, proposes increasing the bit-power allocation algorithm in terms of transmission power is limited finally. The algorithm allocates the largest part of power to the sub-channels which have maximum eigenvalue by calculating the peak power of all sub-channels to meet the target bit error rate, improve the use efficiency of transmission power and the capacity of the system obviously.(5) The propagation characteristics of guided electromagnetic wavesThe actual roadway of the mine contains a lot of axial conductors such as cables, pipes, rails and power lines. The reliable solution is setting up one or more of guided-wave cable in order to achieve low-loss, long-distance transmission. This paper analyzes the propagation characteristics of guided electromagnetic waves in the roadway, simplifies the description of the complex cable surface boundary conditions of underground roadway with surface impedance approximate method of thin wire, derives the approximate solution of guided wave transmission attenuation in roadway which contains axial conductors using approximate method of thin cable, finally, this paper Studies the transmission characteristics of leaky coaxial cable, analyzes the propagation characteristics of single-mode and two-wave-mode, and derives the wave equation of two-wave model.